1. Field of the Invention
This invention relates to optical housing assemblies, particularly a low cost, light weight housing for binoculars in which (a) the interpupillary distance is adjusted by sliding movement between two optically coordinated monocular housings and (b) the optical path in each monocular housing includes mirrors between the objective lens and eyepiece.
2. Description of the Prior Art
Sporting events, athletic and outdoor activities often take place at a significant distance from a spectator. Optical magnification devices, especially binoculars and field glasses, have been proposed and designed to enable a spectator to more clearly view such activities. However, these devices have certain practical drawbacks in providing a clearer, closer view of an event, particularly if a light weight, inexpensive, but effective product is desired.
Dual-path optical systems are well-known in the optical arts and include two general classes of devices, (a) binoculars and field glasses (collectively binoculars), and (b) bioculars. Binocular devices include any instrument in which both eyes are used to view an image to achieve stereoscopic effects or to facilitate observation. They are characterized by having two mechanically linked, but optically uncoupled optical paths, to provide separate twin outputs to the visual system. Stereoscopic perspective is, more or less, commonly present in such devices so that an observer sees objects from slightly different points of view to permit the perception of depth and dimension.
The most common biocular devices are those which are designed so that both eyes view an object through a single objective lens, i.e., there is a single input and a twin output. They are different from binocular devices in that whereas binocular devices send different images to both eyes, biocular devices send the same image to both eyes. Examples of biocular devices are shown and described in U.S. Pat. No. 4,392,710.
In both biocular and binocular devices proper image orientation and proper image alignment is normally desired and achieved through the use of elaborate erecting systems in conjunction with suitable objectives and eyepieces.
In general, binoculars fall into two categories: expensive prismatic devices and less expensive, non-prismatic devices. Prismatic devices use prisms to invert the image. They tend to provide high levels of magnification and clarity. The optical system commonly used in prism binoculars comprises double Porro prisms in conjunction with modified Erfle eyepieces and achromatic doublet objectives. Such systems are relatively expensive and difficult to fabricate because of the tolerances required in manufacture and alignment of the various components, especially the prisms, where angular errors can be introduced at each surface.
Thus binoculars which contain prisms are relatively expensive and due to the use of large grass components, heavy. They are cumbersome to carry, often being worn around the neck of the user on a strap or kept in a case until ready for use. Also, the expense of these binoculars may cause a sense of apprehension in using them for just any event. For these reasons, prismatic binoculars are often not taken to sporting events or athletic activities.
Non-prismatic binoculars, generally referred to as opera glasses, utilize a pair of Galilean telescopes. Galilean telescopes do not require an image inverting device, and are thus potentially very inexpensive. However, the exit pupil of the Galilean telescope is coplanar with the eye lens. The lack of eye relief, greatly limits the usable field of view. Thus, opera glasses are generally produced with magnification, in the range of 2-3.times.. While high power Galilean telescopes may be produced, the very small usable field of view makes them of limited utility for general use.
Consequently, there is a need for a moderate power, high image quality binocular that is relatively inexpensive so that it may be retailed to a large segment of the population for use at popular attractions such as theater, concert, and sporting events.
High quality optical elements exist with precise flatness in mirrors. Precision curvatures in lenses provide excellent resolution in optical systems in cameras, binoculars and projectors, and in other image reducers, expanders and reproducers.
High quality optical objective and eyepiece lenses and mirrors are currently available at low cost. To use those low cost lenses and mirrors in optical equipment and to provide the resolution of which those low cost elements are possible requires precision in their placement within the housings containing the optical system.
It has also been previously known to replace the prisms in binoculars with flat mirrors. Such binoculars are typically shown in Beech U.S. Pat. Nos. 3,985,421, 4,488,790 and 4,758,077. Recognizing the need to initially position and maintain a high degree of accuracy in the placement of all the optical components, as well as to permit subsequent adjustment for the user's individual eyesight and interpupillary spacing, the housings for such prior binoculars having a high image quality and at least a moderate degree of magnification have been relatively complex and expensive.
To obtain good resolution and to fully use the capabilities of the optical systems, precise light paths must be established and maintained between the elements. The disclosed binocular optical system includes four mirrors in the optical path of each monocular housing.
The housings must be mechanically linked together for precise adjustment of interpupillary distance but are otherwise optically uncoupled in that each represents an independent optical path for the associated eye, not sharing any optical components with the other.
As a consequence of the overall architecture, mirror arrangements, and size of optical lens elements used, the interpupillary distance is adjustable with a generally horizontal rectilinear sliding action while at the same time maintaining proper optical alignment between the otherwise uncoupled optical paths corresponding to the left and right eyes. Moreover, provision is made for movement of one or more of either the objective lenses or eyepieces to provide for proper alignment between the left and right eye paths.
Misalignment of optical paths or a slight variation in lengths of optical paths between lenses may greatly reduce the resolution and image qualities of which the optical elements are capable. Thus, some adjustment should be provided to properly orient the two light paths. The housings must also be capable of restricting ambient light which might interfere with the internal light paths.
Compact binoculars have been proposed in which elements of the binoculars are movable outward to a usable position and inward to a stored position to reduce the size for carrying.
Outward and inward movement require fine definition of bearing surfaces and the use of expensive bearing materials to maintain perfect alignment between the optical paths in the binoculars.
A need exists for a low cost, high precision housing for precise positioning of the multiple optical elements forming the optical path. A further need exists for such a housing to include a low cost and easily manipulated bearing adjustment means which will allow (a) outward and inward positioning of the optical elements and (b) the interpupillary distance to be varied in a binocular having optical paths which are being maintained in precise alignment.